Catalytic dehydrohalogenation of alkyl halides in presence of nitrogen-containing compounds



United States Patent 3,326,998 CATALYTIC 'DEHYDROHALOGENATION 0F ALKYL HALIDES IN PRESENCE OF NITRO- GEN-CONTAINING COMPOUNDS Robert E. Reusser and Reagan T. Wilson, Bartlesville,

Okla, assignors to Phillips Petroleum Company, a corporation of Delaware No Drawing. Filed Apr. 20, 1964, Ser. No. 361,295 12 Claims. (Cl. 260677) This invention relates to a process for the dehydrohalogenation of alkyl halides. In another aspect, this invention relates to a process for the dehydrohalogenation of alkyl halides to form olefins.

Currently considerable interest and much research effort have been devoted to the production of biodegradable detergents. A proposed method comprises halogenatconsiderable isomerization of the carbon skeleton of the produced olefins results. While for some uses this is not damaging, branched olefins are of little value when it is desired to form biodegradable detergents via alkylation for reasons previously stated.

Accordingly, an object of our invention is to provide an improved process for the dehydrohalogenation of alkyl halides.

Another object of our invention is to provide a process for the dehydrohalogenation of straight chain alkyl halides to produce straight chain olefins.

Another object of our invention is to provide a process for the dehydrohalogenation of straight chain alkyl halides wherein carbon skeleton isomerization is minimized.

Other objects, advantages and features of our invention will be readily apparent to those skilled in the art from the following description and the appended claims.

We have discovered that in the dehydrohalogenation of alkyl halides to olefins, the formation of branched chain olefins through isomerization is minimized by the introduction of a nitrogen-containing compound selected from the group consisting of ammonia, amines, and nitrosubstituted hydrocarbons into the dehydrohalogenation zone.

The quantity of nitrogen-containing compound introduced into the dehydrohalogenation zone will preferably range from 0.1 to 2.5 weight percent based on the alkyl halide feed to the dehydrohalogenation zone, although concentrations outside this range can be employed. The nitrogen-containing compound will normally contain from 1 to 20 carbon atoms and will be selected from the group consisting of ammonia, primary amines, secondary amines, tertiary amines, and nitro-substituted hydrocarbons, including nitro-substituted aromatics, paraflins, cycloparaffins, cycloolefins, and olefins, preferably nitro-substituted hydrocarbons containing one substituent nitro group.

Some specific examples of nitrogen-containing compounds which can be introduced into the dehydrohalogenation zone are: ammonia, methylamine, diethylamine, tri-n-butylamine, n-octylamine, isopropylamine, tertiarybutylamine, n-decylamine, eicosylamine, aniline, cyclohexylamine, bendylamine, p-tolyla-mine, methylcyclohexylamine, pyridine, Z-ethyl-Sethylpyridine, N-methylpiperi- 3,326,998 Patented June 20, 1967 dine, ethylenediamine, 1,4diaminobutane, 1,2,3-triaminopropane, diethylenetriamine, nitromethane, nitroethane, nitrooctane, nitrodecane, nitroeicosane, nitrobenzene, nitrocyclohexane, nitrocyclopentane, 4-nitrobutene-1, and the like. The particular nitrogen-containing compound selected should preferably have a boiling point sufficiently higher or lower than the reaction products to permit ready separation from the reaction products.

Alkyl halides which are dehydrohalogenated according to the process of this invention normally contain from 3 to 18 carbon atoms. The invention is applicable to the dehydrohalogenation of halogenated alkanes, including monoand polyhalosubstituted alkanes of the straight chain and branched chain type. The invention is particularly applicable to the dehydrohalogenation of straight chain alkyl halides. The alkyl halides which are dehydrohalogenated can be chlorides, iodides, bromides and fluorides. However, the invention is particularly applicable to the dehydrohalogenation of alkyl chlorides. Some specific examples of alkyl halides which can be dehydrohalogenated by the process of this invention are: n-butyl chloride, n-hexyl bromide, n-octyl iodide, n-methyl iodide, n-dodecyl chloride, 4-chlorododecane, 6-chlorotetradecane, n-octadecyl bromide, and the like, including mixtures of two or more of such alkyl halides as occur from the halogenation of n-paraffin mixtures such as 1,4-dichlorobutane, 1,3-dibromohexane, 2,4-dichlorooctane, 1,3,5-trichlorododecane, and 2,4,6,8-tetrachlorooctadecane.

The dehydrohalogenation is conducted as a catalytic dehydrohalogenation process, employing such dehydrohalogenation catalysts as alumina, silica-alumina, oxidized charcoal, bauxite, leaching earth, and the like. A preferred dehydrohalogenation catalyst which is em ployed in the process of this invention is an oxidized activated charcoal. The charcoal portion of the oxidized activated charcoal catalyst is a conventionally activated charcoal such as is prepared from such sources as bagasse, bones, coconut shells, corn cobs, cottonseed hulls, fruit pits, lignin, lignite, nut shells, peat, petroleum coke, sawdust, and the like. After initial carbonization, such as by heating in the absence of air at about 600 C., the charred material is activated by such means as continued heat treating, treatment at elevated temperatures with CO steam, chlorine, S0 etc. By activation, the charcoal is given an extended surface area.

The preferred oxidized charcoal dehydrohalogenation catalysts which are employed in our inventive process are prepared by subjecting an activated charcoal to oxidizing treatment, said oxidizing treatment being carried out by heating the activated charcoal and air to a temperature above about 300 C., preferably to a temperature in the range of from 500 to 700 C. At these temperatures, the time of treatment will vary between about 1 second to about 1 hour, but will generally range from about 1 to 15 minutes. Some minor loss of carbon usually occurs during the oxidation step. If desired, the air employed for the oxidizing treatment may be diluted with gases to better control the treatment and to minimize combustion losses. When oxidized, activated charcoal, the preferred catalyst, is employed, the particle size will normally vary from smaller than 325 mesh (U.S. series) to granules of 6 mesh or larger. Granular material is favored for continuous fixed bed type reactions.

The dehydrohalogenation process can be conducted as a batch or continuous process, utilizing either liquid phase or vapor phase operation. Preferably, the process is conducted in the vapor phase and it is further preferred to operate continuously by passing a mixture of the volatilized alkyl halide and volatilized nitrogencontaining compound through a bed of the dehydrohalogena- 3 tion catalyst at a rate selected to provide the desired degree of conversion. Although preferably the nitrogencontaining compound is mixed with the alkyl halide feed and the mixture passed to the dehydrohalogenation zone,

glowing charcoal. After about 5 minutes of such treatment, the tray was set out to cool and reweighed. The prepared charcoal was then employed for the dehydrochlorination of a mixture of primary and secondary dodecyl chlorides,

the invention is not limited thereto. The nitrogen-con- 5 principally secondary chlorides formed by the chlorination taining compound can be introduced directly into the deof n-dodecane.

hyd'rohalogenation zone. Various methods of adding the Both runs were conducted in a 12 ml. quartz catalyst nitrogen-containing compound to the alkyl halide feed can tube to which the charcoal was charged. The quartz tube be employed. For example, the nitrogen-containing com- Was mounted inside a refractory tube which contained pound can be added to the alkyl halide prior to vaporizaelectric heating elements with the entire arrangement tion, or the materials can be separately vaporized and surrounded by one-half inch asbestos insulation. -In each mixed as vapors prior to entering the catalyst bed. run, nitrogen was metered into the reactor under 5 pounds The dehydrohalogenation of the alkyl halides is effected pressure and at a flow rate of 2.4. liters/ hour. The reactor at temperatures of from about 225 to about 500 C. When was heated by means of the electric heaters to 300 C., conducting a batch process, the catalyst concentration 15 and after the reactor stabilized at 300 C., the dodecyl will range from about 0.01 to about 25 weight percent chlorides were charged at a space velocity of 0.6 (LHSV) of the straight chain alkyl halide feed. When conducting through a 6-inch hypodermic needle. These conditions a continuous process, the liquid hourly space velocity were maintained for 30 minutes to establish equilibrium will range from about 0.01 to about 10 volumes of alkyl and were maintained until dehydrohalogenation, as dehalide feed per volume of catalyst per hour. termined by analysis of effluent dropped to 95 percent.

It is within the scope of this invention to employ a When this occurred, the temperature was raised to 350 carrier gas, inert to the reaction process, to assist the C., and when dehydrohalogenation had again dropped flow of products and by-products within the reaction systo 95 percent, the temperature was raised to 400 C. tern. It is also within the scope of this invention that Both dehydrohalogenation runs were conducted by the as the activity of the catalyst decreases, operation at above described procedure. In Run 1, the feed comprises excessively higher temperatures can be employed until dodecyl chlorides, while the feed in Run 2 comprised regeneration of the catalyst as required. the dodecyl chlorides containing 0.5 weight percent of 2- The product olefins are separated from the effiuent methyl-5-ethylpyridine. mixture withdrawn from the reaction zone. The separated Conversions in each of the runs were determined by unreacted alkyl halides and nitrogen-containing comchromatographic analysis on a 10-foot by A-inch dipound can be recycled to the dehydrohalogenation zone. ameter column packed with glass beads coated with di(n- A suitable separation process comprises passing a liquid decyl) phthalate. The liquid effluent was weighed, and efiluent from the dehydrohalogenation zone to a first the dissolved HCl was removed by placing the collected distillation zone wherein dissolved hydrogen halide is eflluent in an oven at 80 C. and 20 mm. Hg absolute separated from the efiluent and the remainder of the pressure for 30 minutes. The stripped liquid was then cffluent passed to a second distillation zone wherein the analyzed for chlorine content and for straight-chain oleolefin product is separated from the unconverted alkyl fin content. The amount of branched hydrocarbons formed halides and nitrogen-containing compound. by isomerization during dehydroch-lorination was deter- A vaporous effluent withdrawn from the dehydrohalo- I mined by gas-liquid chromatography. The results of these genation zone can be partially condensed and the hydrotests are expressed below in Table I.

TABLE I Feed Percent Wt. Percent Percent Wt. Percent Percent Wt. Percent Dehydro- Branched Dehydro- Branched Dehydro- Branched halogenation Chain halogenation Chain halogcnation Chain Run 1. 99.1 10.1 98. 9 10. 2 99.1 11.8 Run 2. 99. 5 2.8 99. 5 4.8 99. 7 7. 3

gen halide separated from the condensed fraction contain- The results obtained in the dehydrochlorination of ing the olefin product. The condensed fraction can then straight chain dodecyl chlorides when employing a nitrobe subjected to a distillation step as previously described. gen-containing compound clearly demonstrates the eifec- The following specific example is presented, to illustiveness of the nitrogen-containing compound to minimize trate the advantages of the process of this invention and isomerization of the hydrocarbons recovered from the to clearly demonstrate the minimization of the isomerizadehydrogenation zone when compared with the results tion by the addition of a nitrogen-containing compound obtained by dehydrohalogenation of the dodecyl chloto the alkyl halide feed. However, it is not intended rides in the absence of the amine. that the invention should be limited to the features shown Various modifications of this invention can be made, therein. or followed, in view of the foregoing disclosure, without Example departing from the spirit or scope thereof.

Two runs were conducted in which oxidized charcoal We Clam: was employed for the dehydrohalogenation of straight A g which (fompnses mtroducmg a,stralght chain alkyl halides. In Run No. 1, no nitrogen compound c y hahde feed Into qehydrohalogeriatlon q was added to the alkyl halide feed, while in Run No. 2, fzontamfng a dehydrohalogfenanon f' lntroduclflg a Small amount of an amine was added nto said dehydrohalogenation zone a nitrogen-contam- The oxidized charcoal Catalyst employed in these runs mg compound 1n an amount sufiicrent to minimize carbon was prepared by placing a Weighed sample of petroleum skeleton isomerization, and withdrawmg an olefin product base coke in a quartz tray which had been preheated to from Said dehydfohalogenatlon Z0I1e- 50 to 700 C in a uffi f a e Th t was h 2. The process of claim 1 wherein the quantity of said placed in the mufile furnace operating at 650 to 700 C, nitrogencontaining compound introduced into said dehyand the tray rapidly shaken while blowing air over the drohalogenation zone is in the range from 0.1 to 2.5

weight percent based on the alkyl halide feed and the nitrogen-containing compound is selected from the group consisting of ammonia, amines, and nitro-substituted hydrocarbons.

3. The process of claim 2 wherein said dehydrohalogenation catalyst comprises an oxidized activated charcoal.

4. The process of claim 2 wherein the temperature of said dehydrohalogenation zone is maintained in the range from about 225 to about 500 C.

5. The process of claim 4 wherein the dehydrohalogenation process is a batch process and the catalyst concentration is in the range from about 0.01 to about 25 Weight percent of the straight chain alkyl halide feed.

6. The process of claim 4 wherein the dehydrohalogenation process is continuous and the liquid hourly space velocity through said dehydrohalogenation zone is maintained in the range from about 0.01 to about volumes of alkyl halides per volume of catalyst per hour.

7. The process of claim 4 wherein said alkyl halide and said nitrogen-containing compound introduced into said dehydrohalogenation zone are in the vapor phase,

8. The process of claim 7 wherein said alkyl halide feed and said nitrogen-containing compound are mixed prior to the introduction of the mixture into said dehydrohalogenation zone.

9. A process which comprises admixing a straight chain alkyl halide with a nitrogen-containing compound in an amount sufiicient to minimize carbon skeleton isomerization, passing the resulting mixture into a dehydrohalogenation zone containing a dehydrohalogenation catalyst, and withdraw an olefin product from said dehydrohalogenation zone.

10. A process which comprises introducing a straight chain alkyl halide into a dehydrohalogenation zone containing a dehydrohalogenation catalyst, introducing into said dehydrohalogenation zone a nitrogen-containing compound in an amount sufiicient to minimize carbon skeleton isomerization, withdrawing an eflluent mixture from said dehydrohalogenation zone, separating an olefin product from said dehydrohalogenation zone effiuent mixture in a separation zone, and recycling an alkyl halide stream and a nitrogen-containing compound from said separation zone to said dehydrohalogenation zone.

11. The process of claim 1 wherein the straight chain alkyl halide comprises a mixture of primary and secondary dodecyl chlorides.

12. The process of claim 1 wherein the nitrogen-containing compound comprises 2-methyl-5-ethylpyridine.

References Cited UNITED STATES PATENTS 1,056,815 3/1931 Merlinget et a1. 260-680 2,253,323 8/ 1941 Christmann 260-677 2,387,723 10/ 1945 Dreyfus 260-680 2,389,231 11/1945 Blumer 260680 2,553,797 3/1951 Thompson 260680 2,755,322 7/1956 Rust et a1 260680 2,899,473 8/1959 Leprince et al 260-677 3,027,805 9/1965 Gay 260-680 3,227,766 1/ 1966 Kruse 260-677 DELBERT E. GANTZ, Primary Examiner.

ALPHONSO D. SULLIVAN, Examiner. 

1. A PROCESS WHICH COMPRISES INTRODUCING A STRAIGHT CHAIN ALKYL HALIDE FEED INTO A DEHYDROHALOGENATION ZONE CONTAINING A DEHYDROHALOGENATIN CATALYST, INTRODUCING INTO SAID DEHYDROHALOGENATION ZONE A NITROGEN-CONTAINING COMPOUND IN AN AMOUNT SUFFICIENT TO MINIMIZE CARBON SKELETON ISOMERIZATION, AND WITHDRAWING AN OLEFIN PRODUCT FROM SAID DEHYDROHALOGENATION ZONE. 